Method of treating wells



CCL 14 194l D.. M. slMMoNs Filed Aug. l, 1939 ff f 'Wa/ /Lmi 2555-2-1-El METHOD TREATING WELLS INVENTOR ra/y M .immo/7.5

c/ ATTORNEYS .i Patented Oct. 14, 1941 METHOD OF TREATING WELLS Drury'M.Simmons, Shreveport, La., assigner to The Dow Chemical Company, Midland,Mich., a corporation of Michigan Application August 1, 1939, Serial No.287,788

(Cl. 16B-21) 4 Claims.

The invention relates to an improvement in the use of fluid agents,particularly acids, for the treatment of deep wells, such as thoseyielding oil or gas, to increase the production therefrom.

In the treatment of wells with acids it has beenqthe practice, asdescribed in U. S. Patent No. 1,916,122, first to introduce into thewell a quantity of a liquid or solution that is substan' tially inactivetoward the earth formation, which liquid is of a higher specificgravityi than the acid, so as to fill the voids in the earth underlyingthe producing stratum. By such means the acid, when subsequentlyintroduced, is prevented from draining away from the stratum to betreated and spent ineffectively or harmfully on the non-productive earthbelow the producing stratum. Such method however, has certaindisadvantages which clearly limit its usefulness. For example, in somewells the underlying formation is readily permeable to such liquids andthe lattermay flow readily into the underlying earth, so that the acidcannot be maintained in the well in the desired position. In someinstances, as wherein the underlying formation is,y producing water, theacid may increase the per' meability of the water producing formation tothe extent that the water inflow kills the well by preventing the inflowof oil thereinto. An`r other disadvantage is that when fluid pressure isapplied to the acid, as is usually done to force it into the stratum tobe treated, the additional pressure tends to cause the supporting fluidto be' displaced into the formation even though the formation is notreadily permeable, thereby permitting the acid to act uponnon-productive earth or rocobon a stratum that may greatly harm theproducing capacity of the well.

The principal object of the present invention is to provide a means ofintroducing a iiuid treating agent into a well at a desired level Whilepreventing its infiltration into a stratum located at a lower level.Still further objects and advantages of the invention will appear as thedescription proceeds.

I have discovered that these and other objects may be attained byintroducing the fluid treating agent into the well through a conduit,the lower open end of which is located adjacent the producing stratum,while introducing an inac tive liquid into the Well through a secondcon' duit, the lower open end of which is located be-' low that of thefirst conduit.

By the term inactive liquid used herein and in the appended claims ismeant a liquid such reacting with the formation or constituents thereof,and preferably one that is immiscible with the treating agent beingemployed. As an example, when acid is being employed as the treatingagent, crude oil may be suitably employed as the inactive liquid.

The invention then consists in the method hereinafter fully describedand particularly pointed out in the claims, the accompanying drawing andfollowing description setting forth in detail a mode of carrying out theinvention, such mode illustrating however but one of the various ways inwhich the principle of the invention may be carried out.

The single figure of the accompanying drawing is a diagrammatic view invertical section of an oil well suitably equipped for. a treatment inaccordance with the invention. As shown, the upper portion I of the wellbore is cased with metal pipe 2 to a point 3 a short distance above theproducing stratum. The lower portion of the well bore 4 penetrates anoil producing stratum 5 and ends in stratum 6 from which waterencroachment is occurring. Above the ground level, the well is shownequipped with a conventional casing head 1, through which conduit 8, inthis instance the well tubing, extends into the well bore to a point 9adjacent the oil producing stratum 5. Pipes I0 and I I, suitablycontrolled by valves I2 and I3, communicate with the well which waterencroachment is occurring. The

second conduit is sealed to the well tubing above the ground level as bymeans of swagenipple I6. Valve I1, suitably connected to the smallerconduit I4 serves as a means of controlling the introduction of fluidthrough this conduit. The

portion of the well bore adjacent the water stratum is shown filled withan inactive liquid, such as oil I8, while the portion of the boreadjacent the oil stratum is shown filled with acid I9. The remainder ofthe well bore above the oil stratum is shown filled with a pressuringfiuid, such as oil 20, which serves to control the level to which theacid may rise in the well bore.

In carrying out the method of the invention in an oil well having itsproductive stratum disposed in calcareous earth or rock, wherein acid isto be employed to facilitate the production therefrom, the well is firstfilled with oil to render it hydrostatically controllable. This may beacas oil, water, or the like, which is incapable of complished bypumping oil into the well through @cui pipe II while valves I2 and I3are maintained in an open posi-tion. After the well has been filled withoil, the acid solution is started into the well through pipe I Icommunicating with the well tubing 8, while oil is allowed to escape atthe casing head through pipe I0. After a suicient quantity of acid hasbeen introduced to fill the annular space between the tubing 8 andconduit I4, valve I2 controlling pipe I0 is closed and a quantity ofinactive liquid, such as, for ex; ample, oil, is started into the wellthrough conduit I4. During the introduction of the desired amount ofacid, oil or the like is continuously pumped into the well through theconduit I4 and forced into the water stratum 6, thereby preventing theacid from reaching and attacking this formation. After the desiredquantity of acid has been introduced, the well may be closed in to allowthe acid to spend itself. The smaller conduit may then be removed fromthe well and the spent acid 'bailed or pumped from the well,

after which it may be put into production.

By carrying out the treatment in the foregoing manner improved resultsare obtained as regards directing the fluid treating agent into thedesired 'section of the formation, since by bringing about theintroduction of the inactive liquid at a point below the point ofintroduction of the treating fluid, assurance is had that the inactiveliquid is entering the lower portion of the formation while the treatingfluid is conned to the upper portion of the formation.

` Although it is preferable to employ an inactive liquid which isimmiscible with the treating fluid, inactive liquids of the type whichare miscible with the treating agent may also be employed. For example,in carrying out an acid treatment although oil is preferably used, watermay be employed as the inactive liquid, since any mixing that occurswhen the two are pumped into the formation does not detract appreciablyfrom the eifectiveness of the acid solution.

AThe rate at which the two liquids should be introduced relative to oneanother may be varied quite widely, although it is usually preferable tointroduce the inactive liquid at substantially the same rate as thetreating liquid or uid. However, this rate is in turn dependent upon theextent of the formation into which it is desired to prevent the entranceof fluid treating agent relative to the extent of the formation yto betreated.

Although the method has been described with particular reference tocarrying out the acid treatment of a well, it is to be understood thatthe method is also applicable to carrying out a treatment with otheragents, such as parain solvents, chemical plugging agents, and the like,which are in uid form.

Other modes of applying the principle of my invention may be employedinstead of those explained, change being made as regards the meth.. odherein disclosed, provided the step or steps stated by any of thefollowing claims or the equivalent of such stated step or steps beemployed.

I therefore particularly point out and distinctly claim as my invention:

1. In a method of treating a well with a fluid treating agent, said wellbeing equipped with the usual casing and well tubing, the steps whichconsist in introducing the fluid treating agent into the well throughthe well tubing, the lower open end of which is located adjacent theformation to be treated, while introducing an inactive liquid into thewell through a second tubing disposed within the casing and having itslower open end located below that of the well tubing, and forcing boththe fluid treating agent and the inactive liquid into the formationwhile applying pressure on the fluid treating agent through the casingto prevent the upward displacement in the well of the fluid treatingagent as it is being forced into the formation.

2. In a method of treating with hydrochloric acid a well having itsproducing formation 1ocated in calcareous earth or rock formation, saidwell being equipped with the usual casing and well tubing, the stepswhich consist in introducing the acid into the well through the welltubing, the lower open end of which is located adjacent the formation tobe treated, while introducing oil into the well through a second tubingdisposed within the well tubing and having its lower open end locatedbelow that of the well tubing, and forcing both the hydrochloric acidand the oil into the formation while applying pressure upon the acidthrough the casing to prevent its upward displacement in the well boreas it is being forced into the formation.

3. In a method of treating with hydrochloric acid a well having itsproducing formation disposed in a calcareous earth or rock formation,said well being equipped with the usual casing and well tubing, thesteps which consist in introducing the acid into the well through thewell tubing, the lower open end of which is located adjacent theformation to be treated while introducing water into the well through asecond tubing disposed within the well tubing and having its lower openend located below that of the well tubing, and forcing both thehydrochloric acid and the water into the formation while applyingpressure upon the acid through the casing to prevent its upwarddisplacement in the well bore as it is being forced into the formation.

4. In a method of treating a well with a fluid treating agent, the stepswhich consist in introducing the fluid treating agent into the wellthrough a conduit disposed within the well bore and having its open endadjacent the formation to be treated, while introducing an inactiveliquid into the well through a second conduit disposed within the wellbore and having its lower open end located below that of the rst conduitand controlling the rate of introduction of the inactive liquid so as toconduct the uid treating agent to the desired portion of the formation.

DRURY M. SIMMONS.

